Can I use something similar to the ParticleInfo Node but for meta objects?
You could color your Metaballs easily with the Point Density Texture/Map. I recently found it works also great on surface coloring just like the volume coloring. You could set the Radius in the Point Density settings high enough to reach the surface of the Metaballs and it should work properly.

EDIT:

I just tried it myself and it actually works. When you use the Point Density in the Material of the Metaball you have to select the Object with the Particle System on it and make the Radius high enough. You can also select if you want to know the speed or the age of the Particle. Also Cubic Interpolation is much more beautiful in my opinion so select that.